Nanoparticle Effects on Ice Plant Mineral Accumulation under Different Lighting Conditions and Assessment of Hazard Quotients for Human Health.

Nanotechnologies can improve plant growth, protect it from pathogens, and enrich it with bioactive and mineral substances. In order to fill the lack of knowledge about the combined environmental effects of lighting and nanoparticles (NPs) on plants, this study is designed to investigate how different HPS and LED lighting combined with CuO and ZnO NPs influence the elemental composition of ice plants (Mesembryanthemum crystallinum L.). Plants were grown in hydroponic systems with LED and HPS lighting at 250 ± 5 µmol m-2 s-1 intensity, sprayed with aqueous suspensions of CuO (40 nm, 30 ppm) and ZnO (35-45 nm, 800 ppm) NPs; their elemental composition was measured using an ICP-OES spectrometer and hazard quotients were calculated. LED lighting combined with the application of ZnO NPs significantly affected Zn accumulation in plant leaves. Cu accumulation was higher when plants were treated with CuO NPs and HPS illumination combined. The calculated hazard quotients showed that the limits are not exceeded when applying our selected concentrations and growth conditions on ice plants. In conclusion, ice plants had a more significant positive effect on the accumulation of macro- and microelements under LED lighting than HPS. NPs had the strongest effect on the increase in their respective microelements.

Response of Oxidative Stress and Antioxidant System in Pea Plants Exposed to Drought and Boron Nanoparticles.

Pea plants are sensitive to water shortages, making them less attractive to farmers. Hoping to reduce the adverse effects of drought on peas and considering the benefits of boron, this study aimed to investigate the impact of boron nanoparticles on the antioxidant system and oxidative stress biomarkers in drought-stressed peas. Experiments were performed in a greenhouse. Pea plants were treated with a suspension of B2O3 nanoparticles at 12.5, 25, and 50 ppm concentrations before ten days of water shortage. Drought effects were induced by maintaining 30% substrate moisture. This study investigated the properties of the nanoparticle suspension and different application methods for spraying and watering pea plants. The effects of B2O3 nanoparticles and drought were determined on pea growth indicators, oxidative stress biomarkers, and enzymatic and non-enzymatic antioxidants. Spraying with B2O3 nanoparticles at 12.5 ppm most effectively stimulated phenol accumulation; FRAP, DPPH, and ABTS antioxidant capacity; and APX, SOD, GPX, and CAT enzyme activity in pea leaves exposed to drought. In addition, B2O3 nanoparticles reduced the amount of MDA and H2O2 in pea plants grown on a substrate with insufficient moisture. The most substantial positive effect was found on peas affected by drought after spraying them with 12.5 ppm of B2O3 nanoparticles. B2O3 nanoparticles positively affected the pea height, leaf area, number of nodules, and yield.

Photosynthetic Photon Flux Density Effects on Portulaca olearacea in Controlled-Environment Agriculture.

This study aims to evaluate the impacts of the lighting photosynthetic photon flux density (PPFD) on the growth, photosynthesis, and antioxidant response of common purslane (Portulaca oleracea) cultivars to determine energy-efficient lighting strategies for CEA. Green and golden purslane cultivars were cultivated in CEA chambers and four experimental treatments consisting of PPFDs of 150, 200, 250, and 300 ± 10 µmol m-2s-1 were performed, representing daily light integrals (DLIs) of 8.64-17.28 mol m-2d-1 throughout a 16 h photoperiod. The results show that photoresponses to light PPFDs are cultivar-specific. The green cultivar accumulates 174% more dry weight at 300 PPFD compared to the golden cultivar, and also has a higher LUE, but a lower ETR. Dry weight accumulation, plant height, and leaf area dependence on light intensity do not highlight the economic significance of light PPFD/DLI. The derivative parameter (Δ fresh weight (%)/ΔDLI %) more efficiently explains how the percentage increase in DLI due to an increased PPFD affects the percentage of biomass gain between these PPFD treatments. For both cultivars, the relative fresh weight gain is maximal when the lighting PPFD increases from 200 to 250 µmol m-2s-1 and declines with PPFD increases from 250 to 300.

Effect of Light Intensity on the Growth and Antioxidant Activity of Sweet Basil and Lettuce.

Light and nutrients are among the most important factors for sustained plant production in agriculture. As one of the goals of the European Green Deal strategy is to reduce energy consumption, greenhouse growers focus on high-value crop cultivation with less-energy-demanding growing systems. This study aimed to evaluate the effect of fertilization at different light intensities on the growth of lettuce and basil and the activity of the antioxidant system. Sweet basil (Ocimum basilicum, 'Opal') and lettuce (Lactuca sativa, 'Nikolaj') were grown in a greenhouse supplementing natural light (~80 µmol m-2 s-1) with lighting at two photon flux densities (150 and 250 µmol m-2 s-1), 16 h photoperiod, and 20/16 °C day/night temperature in May (Lithuania, 55°60' N, 23°48' E). In each light regime treatment, half of the plants were grown without additional fertilization; the other half were fertilized twice a week with a complex fertilizer (NPK 3-1-3). The results showed that the antioxidant activity of basil was most affected by 150 µmol m-2 s-1 PPFD lighting and the absence of fertilization. Altered antioxidant activity in lettuce in the presence of 250 µmol m-2 s-1 PPFD additional light intensity and fertilization resulted in higher morphological parameters.

Defense response of strawberry plants against Botrytis cinerea influenced by coriander extract and essential oil.

Essential oils and extracts are investigated in sustainable plant protection area lately. Alternative antifungal substances are especially relevant for major economic-relevance pathogens, like Botrytis cinerea (causal agent of strawberry grey mold), control. However, the reaction of plants to alternative protection with plant-origin products is currently unknown. Induced stress in plants causes changes in antioxidant and photosynthetic systems. The aim of the research was to determine the defense response of strawberry plants under application of coriander seed products. In the first step of the research, we determined coriander seed (Coriandrum sativum), black seed (Nigella sativa) and peppermint leaf (Menta × piperita) products' antifungal activity against B. cinerea in vitro. Secondly, we continued evaluation of antifungal activity under controlled environment on strawberry plants of the most effective coriander seed products. Additionally, we evaluated the antioxidant and photosynthetic parameters in strawberries, to examine the response of plants. Antifungal activity on strawberries was determined based on grey mold incidence and severity after application of coriander products. Impact on photosynthetic system was examined measuring photosynthetic rate, transpiration rate, stomatal conductance, and intercellular to ambient CO2 concentration. Strawberry leaves were collected at the end of the experiment to analyze the antioxidant response. The highest antifungal activity both in vitro and on strawberries had coriander seed essential oil, which decreased grey mold severity. Coriander extract increased the photosynthetic capacity and antioxidant response of strawberry plants, however had negative effect on suppression of grey mold. In most cases, the essential oil activated antioxidant response of strawberry plants lower than extract. Our study results provide no direct impact of increased photosynthetic capacity values and antifungal effect after treatment with natural oils. The highest concentrations of coriander essential oil and extract potentially demonstrated a phytotoxic effect.

Phenolic Compounds Content Evaluation of Lettuce Grown under Short-Term Preharvest Daytime or Nighttime Supplemental LEDs.

The study aimed to determine the changes in phenolic compounds content in lettuce (Lactuca sativa L. cv. Little Gem) depending on the preharvest short-term daytime or nighttime supplemental light-emitting diodes (LEDs) to high-pressure sodium lamps (HPS) lighting in a greenhouse during autumn and spring cultivation. Plants were grown in a greenhouse under HPS supplemented with 400 nm, 455 nm, 530 nm, 455 + 530 nm or 660 nm LEDs light for 4 h five days before harvest. Two experiments (EXP) were performed: EXP1-HPS, and LEDs treatment during daytime 6 PM-10 PM, and EXP2-LEDs treatment at nighttime during 10 AM-2 PM. LEDs' photosynthetic photon flux density (PPFD) was 50 and HPS-90 ± 10 µmol m-2 s-1. The most pronounced positive effect on total phenolic compounds revealed supplemental 400 and 455 + 530 nm LEDs lighting, except its application during the daytime at spring cultivation, when all supplemental LEDs light had no impact on phenolics content variation. Supplemental 400 nm LEDs applied in the daytime increased chlorogenic acid during spring and chicoric acid during autumn cultivation. 400 nm LEDs used in nighttime enhanced chlorogenic acid accumulation and rutin during autumn. Chicoric and chlorogenic acid significantly increased under supplemental 455 + 530 nm LEDs applied at daytime in autumn and used at nighttime-in spring. Supplemental LEDs application in the nighttime resulted in higher phenolic compounds content during spring cultivation and the daytime during autumn cultivation.

Effect of Different Ratios of Blue and Red LED Light on Brassicaceae Microgreens under a Controlled Environment.

The consumption of microgreens has increased due to their having higher levels of bioactive compounds and mineral nutrients than mature plants. The lighting conditions during the cultivation of microgreens, if optimally selected, can have a positive effect by further increasing their nutritional value. Thus, our study aimed to determine the changes in mineral nutrients contents of Brassicaceae microgreens depending on different blue-red (B:R) light ratios in light-emitting diode (LED) lighting and to evaluate their growth and nutritional value according to different indexes. Experiments were performed in controlled environment growth chambers at IH LRCAF, 2020. Microgreens of mustard (Brassica juncea 'Red Lace') and kale (Brassica napus 'Red Russian') were grown hydroponically under different B:R light ratios: 0%B:100%R, 10%B:90%R, 25%B:75%R, 50%B:50%R, 75%B:25%R, and 100%B:0%R. A 220 µmol m-2 s-1 total photon flux density (TPFD), 18 h photoperiod, 21/17 ± 2 °C temperature and 60% ± 5% relative humidity in the growth chamber were maintained during cultivation. We observed that an increasing percentage of blue light in the LED illumination spectrum during growth was associated with reduced elongation in the microgreens of both species and had a positive effect on the accumulation of mostly macro- and micronutrients. However, different B:R light ratios indicate a species-dependent response to changes in growth parameters such as leaf area, fresh and dry mass, and optical leaf indexes such as for chlorophyll, flavonol, anthocyanin, and carotenoid reflectance.